3.10.2.3
Compressive Strength Tests
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NOTE: When the same mix design is used for multiple
elements such as slabs, beams, and walls, the design
element type may be specified in lieu of or in
addition to the mix design in order to better
identify deficient concrete.
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ASTM C 39. Make five test cylinders for each set of tests in accordance
with ASTM C 31/C 31M. Precautions shall be taken to prevent evaporation
and loss of water from the specimen. Test two cylinders at 7 days, two
cylinders at 28 days, and hold one cylinder in reserve. Samples for
strength tests of each [mix design of] [and for] [_____] concrete placed
each day shall be taken not less than once a day, nor less than once for
each 120 cubic meters (100 cubic yards) 100 cubic yards of concrete, nor
less than once for each 500 square meters (5000 square feet) 5000 square
feet of surface area for slabs or walls. For the entire project, take no
less than five sets of samples and perform strength tests for each mix
design of concrete placed. Each strength test result shall be the average
of two cylinders from the same concrete sample tested at 28 days. If the
average of any three consecutive strength test results is less than f'c or
if any strength test result falls below f'c by more than 3 MPa (500 psi)
500 psi, take a minimum of three ASTM C 42/C 42M core samples from the
in-place work represented by the low test cylinder results and test.
Concrete represented by core test shall be considered structurally adequate
if the average of three cores is equal to at least 85 percent of f'c and if
no single core is less than 75 percent of f'c. Locations represented by
erratic core strengths shall be retested. Remove concrete not meeting
strength criteria and provide new acceptable concrete. Repair core holes
with nonshrink grout. Match color and finish of adjacent concrete.
[3.10.2.4
Air Content
ASTM C 173/C 173M or ASTM C 231 for normal weight concrete [and ASTM C
173/C 173M for lightweight concrete]. Test air-entrained concrete for air
content at the same frequency as specified for slump tests.
][3.10.2.5
Unit Weight of Structural Lightweight Concrete
ASTM C 567. Determine unit weight of lightweight concrete.Perform test for
every 15 cubic meters (20 cubic yards) 20 cubic yards maximum.
][3.10.2.6
Ion Concentration
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NOTE: Include only when justified by size of job or
when quality of concrete is questionable.
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ACI 318M/318RM. Determine water soluble ion concentration.
Perform test
once for each mix design.
]
-- End of Section --
SECTION 03300N
Page 46
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